1. Field
The present invention relates to an information processing apparatus, a fuel cell unit and a program updating method thereof, and particularly relates to an information processing apparatus having a fuel unit, a fuel cell unit and a program updating method thereof.
2. Description of the Related Art
Currently, lithium ion batteries and the like are used as secondary cells, which is a type of electric power supply source for information processing apparatuses. One feature of secondary cells is the ability to be repeatedly charged and reused by means of a commercial power source, which is a feature that disposable primary cells do not have. Accordingly, lithium ion batteries need to be charged using such a commercial power source, being a secondary cell.
Also, the improvement in capabilities of information processing apparatuses in recent years has been tremendous, and accordingly the electric power consumption of information processing apparatuses is on the rise. Efforts are being made to increase the density of energy which lithium ion batteries provide as electric power to the information processing apparatuses, i.e., the amount of output energy per unit volume or per unit mass, but marked improvement thereof is unlikely.
On the other hand, the energy density of fuel cells is said to be logically calculated to be ten times that of lithium ion batteries (e.g., see “Fuel Cell 2004 (Nenryou-Denchi 2004)” Nikkei Business Publications, Inc., pp. 49-50 and pp. 64, October 2003). This means that a fuel cell has the potential to supply electric power for longer time (e.g., ten times) with the same volume or mass. Conversely, a fuel cell has the potential to supply electric power for the same amount of time with a far smaller and lighter cell than a lithium ion battery.
Also, a fuel cell can be formed into a unit wherein fuel such as methanol or the like is sealed in a small container, with this small container being replaced whenever necessary, meaning that there is no need for external charging. Accordingly, information processing apparatuses such as notebook computers can be used for far longer periods of time by obtaining electric power using the fuel cell as compared with lithium ion batteries in situations where there are no AC power facilities. In other words, using lithium ion batteries places restrictions on using such information processing apparatuses, either on the amount of time of continuous use, or on the environment, since using for long periods of time requires availability of an AC power source.
In light of the above, research and development of fuel cells for supplying electric power to information processing apparatuses is being carried out, as disclosed in, for example, JP-A 2003-142137 and JP-A 2002-169629.
While there are various types of fuel cells (e.g., see “Everything of Fuel Cell (Nenryoudenchi-no-subete),” Hironosuke Ikeda, Nippon Jitsugyo Publishing Co., Ltd., August 2001), the Direct Methanol Fuel Cell (DMFC) type is a suitable candidate for use with information processing apparatuses, from the perspective of size, weight, and further, ease of handling the fuel. This type of fuel cell uses methanol for fuel, and the methanol does not have to be converted into hydrogen but is directly injected to the fuel electrode.
With Direct Methanol Fuel Cells, the concentration of the methanol injected to the fuel electrode is crucial, and in the event that the concentration is high the generating efficiency is poor and sufficient capabilities cannot be obtained. This is due to a phenomenon called “crossover” wherein a part of the methanol serving as fuel permeates a electrolytic film (solid polymer electrolytic membrane) between the fuel electrode (negative electrode) and air electrode (positive electrode). This crossover phenomenon becomes marked in the event that the methanol is highly concentrated, and is reduced in the event that low-concentration methanol is injected to the fuel electrode.
On the other hand, while using low-concentration methanol as fuel readily yields high performance, the volume of fuel becomes greater than cases of using high-concentration methanol (e.g., ten times), so the fuel storage container (fuel cartridge) is large in size.
An arrangement can be made to deal with this problem, wherein high-concentration methanol is stored in the fuel cartridge to reduce the size of the cartridge, and at the same time using small-sized pumps, valves, etc., for recirculation of water generated at the time of generating electricity so as to reduce the concentration of the high-concentration methanol before injecting to the fuel cell, thereby reducing the crossover phenomenon and improving electric power generating efficiency. In the following description, the pumps, valves, etc., used for recirculation will be referred to as “auxiliaries”, and this system for recirculation of the water will be referred to as “dilution-recirculation system”.
Such an approach (as disclosed in “Fuel Cell 2004 (Nenryou-Denchi 2004)” Nikkei Business Publications, Inc., pp. 49-50 and pp. 64, October 2003) can achieve a compact, lightweight fuel-cell unit having high power-generation efficiency.
Information processing apparatuses having fuel cell units, particularly portable type information processing apparatuses which do not receive supply of electric power from commercial power sources, are capable of operating for longer hours than those using secondary cells of the electric power source.
However, information processing apparatuses having fuel cell units need control specially for the fuel cell unit. For example, in order to obtain predetermined generating efficiency, the amount and concentration of fuel injected to the fuel cell, or the amount of air (oxygen), needs to be suitably controlled by driving multiple auxiliaries.
Further, it is important to monitor information of the fuel cell unit, such as fuel cell unit identification information, identification information of the fuel itself, information regarding the amount of fuel remaining, and so forth, and to provide this information to the user of the information processing apparatus, for example.
Controlling the auxiliaries, monitoring the information, and the like, can be effectively realized by a control method wherein a control program is executed by a micro-computer, for example.
Generally, with a system using software such as control programs or the like, the functions and performance of the overall system can be improved by changing the software alone, without changing the hardware. Also, cases can be conceived wherein the type of fuel itself used for the fuel cell unit is changed in order to improve the electric power generating efficiency, which could lead to the need to change the identification information of the fuel itself which the control program holds.
Though various methods can be conceived for changing the control program, a system wherein the user of the information processing apparatus obtains an updating control program via an electric communication line such as the Internet or the like, and installs the control program himself/herself, would be extremely handy for the user.
Also, with information processing apparatuses having fuel cell units, the fuel cell unit itself cannot be controlled while updating the control program for the fuel cell unit. Accordingly, there is the need to obtain electric power necessary for updating the control program other than from the electricity generated by the fuel cell unit, since the fuel cell unit needs to stop generating electricity before updating the control program.